In general, artificial breast prostheses are used in reconstructive plastic surgery for a breast when breast loss occurs due to diseases or accidents and in cosmetic surgery for a malformed breast. In terms of anatomy, artificial breast prostheses are also used for the substitution of organs or tissues.
Artificial breast prostheses are products in which a filling material, such as saline, hydro-gel, and silicone gel, is filled in an envelope formed of silicone that is implantable to an organ (hereinafter referred to as a “shell”). These artificial breast prostheses may be classified into round products and water drop shaped products according to the shape of a product, and may be classified into smooth products and textured products according to the surface conditions of a product. More particularly, the artificial breast prostheses will be described in brief as follows.
A saline filled artificial breast prosthesis is configured such that saline is injected or is injectable into a shell formed of silicone (more particularly, the shell being formed of polyorganosiloxane, such as polydimethylsiloxane or polydiphenylsiloxane). The saline filled artificial breast prosthesis has a structure consisting of a silicone shell and a valve.
Although the saline filled artificial breast prosthesis ensures safety of a user even if the filling material leaks into the human body after rupture of the shell as a result of using sterile saline as the filling material, and is easy to change the volume of a breast by adjusting the injection amount of saline, the saline filled artificial breast prosthesis is significantly deteriorated to the touch after surgery as compared to other artificial breast prostheses and the shell thereof has inferior durability.
A hydro-gel filled artificial breast prosthesis is configured such that hydro-gel composed of monosaccharide and polysaccharides is filled within the same shell as that used in the above described saline filled artificial breast prosthesis. The hydro-gel filled artificial breast prosthesis is a product developed based on the principle that the filling material can be absorbed into and excreted from the human body even if the filling material leaks into the human body due to rupture of the shell.
However, in the case of the hydro-gel filled artificial breast prosthesis, safety with respect to long term use has not been established, volume change depending on the lapse of time and occurrence of wrinkles may increase after the artificial breast prosthesis is inserted into the human body, and feeling is unnatural as compared to a silicone gel filled artificial breast prosthesis. At present, the above described hydro-gel filled artificial breast prostheses are not distributed on the market on the basis of the year 2000 due to problems in relation to the proof of safety.
A silicone gel filled artificial breast prosthesis is configured such that silicone gel having an appropriate viscosity is filled in a shell. The silicone gel filled artificial breast prosthesis has very superior product durability and more pleasant texture than the saline filled artificial breast prosthesis, and owing to these advantages, has achieved a dominant position in the market.
The silicone gel filled artificial breast prosthesis has been developed in the order of a first generation prosthesis, a second generation prosthesis, and a third generation prosthesis. This development history will be described in detail as follows.
The first generation silicone gel filled artificial breast prosthesis is a product sold from the middle of the 1960s to the middle of the 1970s, and was initially developed in the year 1961 by Cronin and Gerow. The first generation silicone gel filled artificial breast prosthesis can be represented in brief by use of a thick shell, a smooth surface type, and silicone gel of a high viscosity. This prosthesis has caused gel bleed and capsular contracture, but a rupture speed thereof was relatively low due to the use of the thick shell.
The second generation silicone gel filled artificial breast prosthesis is a product sold from the middle of the 1970s to the middle of the 1980s, and includes a thin shell and a silicone gel filling material of a low viscosity, for the sake of smoother texture. This prosthesis is characterized by a similar gel bleed rate, higher rupture occurrence, and lower capsular contracture as compared to the first generation prosthesis.
The third generation silicone gel filled artificial breast prosthesis is a product sold from the middle of the 1980s to present, and includes a gel bleed barrier layer to prevent gel bleed. The third generation silicone gel filled artificial breast prosthesis includes a thicker shell and silicone gel of a higher viscosity as compared to the second generation prosthesis. In addition, a product having a rough surface has been developed, in order to reduce capsular contracture. The third generation silicone gel filled artificial breast prosthesis exhibit low rupture and low capsular contracture occurrence, as compared to the first and second silicone gel filled artificial breast prostheses.
As defined above, development and progress in terms of artificial breast prosthesis safety have focused on decrease in rupture and capsular contracture. This is a natural result, when taking into consideration the fact that rupture and capsular contracture are the greatest side effects of artificial breast prostheses.
These two side effects, that is, rupture and capsular contracture will be described. First, in the case of rupture, an event in which Dow Corning sold the prosthesis was bankrupted due to rupture of a great amount of the second generation silicone gel filled artificial breast prosthesis using a thin shell is well-known. The filling material (silicone gel) of the artificial breast prosthesis may leak into the body through the ruptured shell, deformation and malfunction of the prosthesis thus occur, and, as a result, the prosthesis is removed.
Second, capsular contracture is a natural biological rejection reaction in which collagen films are firmly accumulated around a prosthesis, after insertion of the implant into the human body, which is observed in all patients that undergo artificial breast prosthesis surgery, but there is a difference in severity of capsular contracture therebetween. Prostheses are removed from patients that suffer from serious capsular contracture.
Considering prosthesis removal operation caused by side effects according to various causes, capsular contracture is known to be the most significant side effect of artificial breast prostheses, which is demonstrated from various clinical papers published for a long time.
In accordance with continuous research and progress of artificial breast prostheses, for capsular contracture which is a side effect having high onset and high re-operation, prostheses capable of reducing the onset and reoperation is developed. As a result, the third generation artificial breast prostheses have emerged, and textured surface artificial breast implants in which the surface thereof is roughly formed or modified in order to reduce capsular contracture were developed and distributed in the market.
Such a textured artificial breast implant minimizes hardening of collagen films deposited on the surface thereof, thus minimizing occurrence of capsular contracture. Various methods to form a rough surface of an artificial breast implant have been developed to date. However, methods having commercial availability are classified into four forms, that is, urethane foam, solid particle, processed mold, and pressed mold forms.
Of these, artificial breast implants in which urethane foams developed by methods described in U.S. Pat. No. 3,366,975 and U.S. Pat. No. 3,683,424 formed on the surfaces thereof are known to exhibit the greatest effects on reduction of capsular contracture, but such a method and product are not used at present due to the problem associated with safety of urethane in the body.
U.S. Pat. No. 4,889,744, U.S. Pat. No. 5,545,220, and U.S. Pat. No. 5,964,803 disclose methods for forming artificial breast implants having a textured (rough) surface, by adhering solid particles to artificial breast shells, or adhering solid particles to artificial breast shells, followed by melting.
U.S. Pat. No. 4,965,430 discloses a method for producing artificial breast implants with a textured surface, by forming a textured surface on a mold used for preparation of an artificial breast implant.
U.S. Pat. No. 4,960,425, U.S. Pat. No. 4,955,909, U.S. Pat. No. 5,022,942, and U.S. Pat. No. 5,236,453 disclose methods for producing an artificial breast implant having a textured surface by adhering a film surface-roughened through a mold or ion beam to an artificial breast shell using a press mold.
Of these methods, except the method of forming a urethane foam on the surface of an artificial breast, other methods simply make the surface of the artificial breast rough and have lower efficacy in terms of reduction of capsular contracture as compared to urethane foam artificial breasts.
The reason for this is that except the method of forming a urethane foam on the surface of to artificial breast, other methods are low in uniform deposition and hardening prevention of collagen films on the surface of implants, as compared to urethane implants, since a textured surface form, more specifically, textured mono-layer, not a foam layer, is formed on the surface of the artificial breast.
As described above, the development and progress in terms of safety of silicone artificial breast implants have focused on decrease in rupture and capsular contracture, but methods developed to date are not complete in technical regards, and in particular, have a high capsular contracture onset as a side effect, thus entailing considerably frequent removal and re-operation of the implants. This fact is clinically demonstrated.
Accordingly, development of artificial breast implants that are capable of reducing capsular contracture and exhibit superior durability remains as a problem that should be urgently and completely solved.